The present invention relates to a method and apparatus for generating On-Screen-Display (OSD) messages using a line doubling mode. More particularly, this invention relates to a method and apparatus that reduces the memory bandwidth requirements of a decoding/displaying system by repeating each OSD line on the next line of video for an OSD region.
On-Screen-Display messages play an important role in consumer electronics products by providing users with interactive information such as menus to guide them through the usage and configuration of the product. Other important features of OSD include the ability to provide Closed Captioning and the display of channel logos.
However, the heightened standard of digital video technology presents an ever increasing problem of generating and displaying OSD messages. For example, there are specific High Definition Television (HDTV) requirements that an HDTV must display up to 216 characters in four (4) xe2x80x9cwindowsxe2x80x9d versus the current National Television Systems Committee (NTSC) requirements of a maximum of 128 characters in one xe2x80x9cwindowxe2x80x9d. These new requirements place severe strains on the decoding/displaying system used to decode and display television signals (e.g., HDTV, NTSC, MPEG, and the like), which must decode the incoming encoded data streams and present the decoded data to a display system with minimal delays. Since OSD messages must be displayed (overlaid) with the video data, the microprocessor of the decoding/displaying system must assign a portion of the memory bandwidth to perform OSD functions, thereby increasing the memory bandwidth requirements of a decoding/displaying system and the overall computational overhead.
Thus, a need exists for a method and apparatus for generating On-Screen-Display (OSD) messages without increasing the hardware requirements, e.g., memory bandwidth, of a decoding/displaying system.
The invention concerns an apparatus and concomitant method for generating OSD messages by constructing a valid OSD bitstream with instructions in the OSD header to repeat each OSD line.
More specifically, in accordance with the invention, an OSD unit retrieves an OSD bitstream from a storage device. The OSD bitstream contains an OSD header and OSD data. The OSD header contains control information that is used to program a color palette of the OSD unit and to provide instructions as to the treatment of the OSD data. The control information is programmed by a processor of a decoding/displaying system. If the xe2x80x9cLine Doubling Modexe2x80x9d is enabled in the OSD header, then the OSD unit will repeat the OSD data such that each OSD line is repeated. An OSD line represents a line of OSD pixels in an OSD region. Thus, the OSD unit receives xe2x80x9cxxe2x80x9d lines of OSD data, and, in turn, displays xe2x80x9c2xxe2x80x9d lines of OSD data.
These and other aspects of the invention will be described with respect to the accompanying drawings.